Research on High-Pressure Hydrochloric Acid Leaching of Scandium, Aluminum and Other Valuable Components from the Non-Magnetic Tailings Obtained from Red Mud after Iron Removal

Dmitry Zinoveev,Darya Grigoreva,Pavel Grudinsky,Anton Volkov,Valery Dyubanov,Ekaterina Zhiltsova,Alexander Petelin

doi:10.3390/met11030469

Abstract

Red mud is a hazardous waste of the alumina industry that contains high amounts of iron, aluminum, titanium and rare-earth elements (REEs). One of the promising methods for the extraction of iron from red mud is carbothermic reduction with the addition of sodium salts. This research focuses on the process of hydrochloric high-pressure acid leaching using 10 to 20% HCl of two samples of non-magnetic tailings obtained by 60 min carbothermic roasting of red mud at 1300 °C and the mixture of 84.6 wt.% of red mud and 15.4 wt.% Na2SO4 at 1150 °C, respectively, with subsequent magnetic separation of metallic iron. The influence of temperature, leaching duration, solid-to-liquid-ratio and acid concentration on the dissolution behavior of Al, Ti, Mg, Ca, Si, Fe, Na, La, Ce, Pr, Nd, Sc, Zr was studied. Based on the investigation of the obtained residues, a mechanism for passing valuable elements into the solution was proposed. It has shown that 90% Al, 91% Sc and above 80% of other REEs can be dissolved under optimal conditions; Ti can be extracted into the solution or the residue depending on the leaching temperature and acid concentration. Based on the research results, novel flowsheets for red mud treatment were developed.

Highlights

Red mud is a solid waste generated during the extraction of alumina from bauxite ores by the Bayer method [1]
It has found that red mud is proved to be a promising material for obtaining coagulants and can be used as an adsorbent for heavy metals in wastewater [5]; it can be utilized in a wide range of catalytic applications [6], as well as for a production of various building materials [7]
We study hydrochloric acid leaching of two different kinds of the tailings after the carbothermic roasting and magnetic separation of red mud

Summary

Introduction

Red mud is a solid waste generated during the extraction of alumina from bauxite ores by the Bayer method [1]. The lack of efficient processing technologies is the main reason why red mud is out of use and accumulated in special sludge storage facilities, which have an adverse impact on the environment and have even led to technogenic catastrophe [3]. It is important to note that the Sc content in red mud is in the range of 0.013 to 0.039% [10], which is quite significant. The actual composition of red mud depends on the bauxite mineralogy and different technological parameters of the Bayer process [11]. The iron content in red mud is comparable with poor iron ore [12], which is an important driver for research on the processing of red mud

Methods

Results

Conclusion